The present invention relates to connectors for tube assemblies, and more particularity, relates to a ferrule-less connectors for tubes in high pressure fluid systems.
Modern instruments and equipment applied in high pressure liquid systems have inherently become more complex. This axiom also applies to tube connectivity and interchangeability where instrument designers are challenged to connect fluid and gas lines easily, reliably and inexpensively.
Generally, compression ferrules are employed as reliable and simple fluid line connections in high pressure liquid systems such as High Pressure Liquid Chromatography (HPLC) and DNA sequencing systems. These compression ferrules are relatively small conical structures which cooperate with one or two-piece tube fittings, such as Poly-Ether-Ether Ketone (PEEK) fittings, to form fluid-tight connections to the instrument tubing. Typical of such compression ferrules fittings are the RHEFLEX(copyright) Precision, Twist-Free and Flangeless PEEK Fittings by Rheodyne, L. P. of Rohnert Park, Calif.
Although these compression ferrules provide simple and reliable fluid connections in high pressure fluid environments, the fabrication costs associated with these devices and their corresponding fittings can quickly escalate as the number of fluid connections multiply. Such devices require precise machining of detailed ports where two fluid lines connect together, or where the fluid lines interconnect to components such as fluid manifolds and valves, for instance. As the number of these fluid interconnections increase, thus, the consequential cost of machined parts, and/or the cost of production tooling increases.
Moreover, modern drag discovery and high throughput screening, which utilize these high pressure liquid systems and instruments, substantially multiply the number of specimens simultaneously sampled. The amount of interconnections quickly becomes problematic. Especially considering that each connection/reconnection typically may require compression ferrule replacement.
With the advent of miniaturization, connecting to the outside world will become even more imperative. Thus, there is an increased need for simple, reliable and cost effective fluid connections for high and low pressure fluid systems.
The present invention provides a high pressure tube assembly adapted for liquid sealing against a rigid surface, having a connecting conduit, in a high pressure liquid application. The tube assembly includes a rigid, elongated, tube member having a spherical sector-shaped distal end portion with a spherical radius substantially larger than the radius of the tube member. The end detail could also be elliptical, parabolic, or machined such that most of the material around the through hole is removed, leaving an easily deformable surface to create a seal with applied force. The tube member includes a central conduit terminating at an apex of the spherical sector-shaped distal end portion to define an annular rim portion such that a fluid-tight seal can be formed between the central conduit of the tube member and the connecting conduit of the surface. This seal is formed at a contact interface between the rim portion and the surface when a relative axial force is applied therebetween.
Accordingly, the greater the axial force, the greater the area of the contact interface as the rim portion increasingly deforms. Consequently, the sealing integrity between rim portion and the rigid surface is increased.
In another aspect of the present invention, a method of forming a high pressure liquid seal against a rigid surface is provided. The method includes providing a rigid, elongated, tube member having a spherical sector-shaped distal end portion with a radius substantially larger than the radius of the tube member. The tube member further includes a central conduit terminating at an apex of the spherical sector-shaped distal end portion to define an annular rim portion. The method of the present invention further includes applying a compression force in al axial direction of the tube member to one of tube member and the rigid surface. This axial force forms a fluid-tight seal between the central conduit of the tube member and the connecting conduit of the surface at a contact interface between the rim portion and the surface.
In yet another aspect of the present invention, a fluid fitting assembly is provided for a fluid-tight coupling to a connecting conduit on a rigid surface of a body member. The fitting assembly includes a connector fitting formed to couple to the body member, and a rigid, elongated, tube member having a central conduit terminating at a contacting end thereof. The tube member is slideably coupled to the connector fitting for sliding movement of the contacting end toward and away from the connecting conduit of the body rigid surface. A biasing device is coupled between the connector fitting and the tube member for biasing the contacting end into abutting contact with the rigid surface. This device generates a biasing force sufficient to form a fluid-tight seal between the central conduit of the tube member and the connecting conduit of the body rigid surface when the connector fitting is coupled to the body member.
In one embodiment, the connector fitting further includes an interior proximal shoulder portion and an interior distal shoulder portion defining the opposed ends of a cavity extending generally coaxial with the tube passage. Further, the biasing device includes a compression spring which is disposed in the cavity. One end of the spring abuts the distal shoulder portion of the connector fitting, while an opposite end is coupled to the tube member to bias the tube member toward the body rigid surface.
In still another aspect of the present invention, a fluid fitting system is included for a High Pressure Liquid device. The fitting system includes a fluid manifold body having a plurality of connecting conduits terminating at a rigid surface, and a connector fitting formed to couple to the manifold body. A plurality of rigid, elongated, tube members are provided with each having a central conduit terminating at a respective contacting end thereof. Each tube member is slideably coupled to the connector fitting for sliding movement of the respective contacting end toward a corresponding connecting conduit of the body rigid surface. A biasing device is coupled between the connector fitting and each tube member for biasing the respective contacting end into abutting contact with the rigid surface. This biasing force is sufficient to form a fluid-tight seal between the central conduit of the tube member and the respective connecting conduit of the body rigid surface when the connector fitting is coupled to the body member.